This invention relates generally to amniocentesis procedures, and more particularly to apparatus and techniques enhancing the accuracy and safety of such procedures.
Amniocentesis is an obstetrical procedure in which a small gauge needle is inserted percutaneously through the uterus into the pregnancy sac to obtain a sample of the amniotic fluid for prenatal genetic and biochemical studies. In order to reduce the possibility of needle injuries to the placenta and the fetus, this invasive procedure is performed under direct vision techniques using ultrasound, as the needle is being inserted through the tissue layers into the pregnancy sac. Both free hand insertion and techniques employing needle guides are presently used. Needle guides are designed to increase the accuracy of the insertion as compared to the free hand technique.
Presently used needle guides are constructed as parts of transducer probes, and because of such attachment, much of the desired maneuverability is lost. An "articulated" needle guide has been described recently (OB-GYN, Vol. 74, No., 1989), but it still has to be attached to the transducer probe itself and thereby offers no maneuverability advantage. Besides, due to the employment of a large number of moving parts (and joints) in this needle guide, the design has defeated its purpose by unnecessarily requiring a large number of variables that need to be adjusted and fixed to properly position the needle, thereby increasing the chance of inaccuracy in setting the needle direction. This also produces considerable clumsiness in its overall application.